Retaining clamp for a disc storage apparatus

ABSTRACT

In the present invention, an improved retaining member for a disc drive is disclosed. The disc drive has a spindle with a plurality of data storage discs mounted on the spindle. The retaining member is in the shape of a ring with a central hole and a plurality of spaced-apart teeth-shaped members positioned circumferentially about the ring and protruding into the central hole. The retaining member is positioned with the spindle through the central hole and substantially abuts one of the data storage discs. The plurality of teeth-shaped members are urged against the side of the spindle.

TECHNICAL FIELD

The present invention relates to a retaining clamp to clamp a pluralityof data storage discs on a rotatable spindle in a disc drive. Theimproved retaining clamp supplies substantially uniform force to thedata storage discs and can be easily removed and applied with A minimalamount of contamination to the data discs.

BACKGROUND OF THE INVENTION

Direct Access Storage Devices (DASD), such as disc drives, arewell-known in the art. A typical prior art disc storage apparatus has abase with one or more data storage discs rotatably mounted on the baseand a motor to rotate the discs. A pivot assembly is mounted on the baseand is fixedly attached to the base at one end of the pivot assembly. Atransducer assembly having one or more transducer heads is mounted onthe pivot assembly at the other end. An actuating means, such as a voicecoil motor, is positioned between the transducer assembly and the fixedend of the pivot assembly. The voice coil motor moves the pivotassembly, thereby moving the transducer assembly with the transducerheads moved over the surface of the discs. See, for example, U.S. Pat.Nos. 4,751,597 and 4,300,176. Although such an arrangement is compact,these prior art devices have suffered from the disadvantage of poorfrequency response.

Further, as glass becomes the choice of consideration for the substrateof the storage discs, in the disc drive, it becomes desirable to retainor hold the glass discs in place, such that the glass will not slip,warp or break. In addition, it is desired to be able to control theamount of the clamping force on the stack of discs. The force cannot beso high as it will break the glass disc, nor it can be so low as tocause the disc to slip under shock and vibration. The clamping forcemust be constant or nearly so with dimensional changes experienced undertemperature variations.

Conventional retaining rings, used in automobiles and agriculturalequipment, purchasable from, for example, Walds Truarch, is well-knownin the art.

Finally, as the size of discs decreases, it becomes increasinglydesirable to use zone band recording, to record magnetic information onthe discs. In zone band recording, different density of recording isachieved at different radius, resulting in a constant number of bytesper track recording. However, zone band recording requires thetransducer head to be at a nearly constant height over the disc surface.In the prior art, one company, DASTech, has proposed the use ofradically-designed transducer heads to maintain the head at a constantor substantially constant flying height over the disc. However, to date,it is not believed that a conventional head can be maintained at aconstant flying height over the surface of the disc.

SUMMARY OF THE INVENTION

In the present invention, a disc storage apparatus having a spindle, aplurality of data storage discs mounted on the spindle and a motorconnected to the spindle for rotating the discs is disclosed. Theimprovement comprises a retaining clamp in a shape of a ring with acentral hole and a plurality of spaced-apart teeth-shaped memberspositioned circumferentially about the ring protruding into the centralhole. The retaining clamp is positioned with the spindle through thecentral hole and with the retaining clamp substantially abutting one ofthe data storage discs with the plurality of teeth-shaped members urgingagainst the side of the spindle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the disc storage apparatus of thepresent invention with the cover removed, showing the major elements ofthe disc storage apparatus.

FIG. 2 is a top view of the disc storage apparatus, shown in FIG. 1,with a pivot assembly being movable about the extreme pivotingpositions.

FIG. 3 is a perspective view of a retaining clamp portion of the discstorage apparatus of the present invention showing the retaining clampin relationship to a spindle to which the data storage discs aremounted.

FIG. 4 is a partial cross-sectional side view of the disc storageapparatus showing the retaining clamp in a retaining position urgingagainst the side of the spindle and against the outermost data storagedisc.

FIG. 5 is the same cross-sectional view as FIG. 4, showing the retainingclamp being inserted, by an insertion tool, on the spindle of the datastorage apparatus of the present invention.

FIG. 6 is the same cross-sectional view as FIG. 4, showing a removaltool in position to remove the retaining clamp from its retainingposition.

FIG. 7 is a bottom perspective view of the removal tool for removing theretaining clamp from its retaining position on the spindle of the datastorage apparatus.

FIG. 8 is a detailed, partial cross-sectional view of the pivot assemblyof the data storage disc apparatus of the present invention.

FIG. 9 is a cross-sectional view of the pivot assembly taken along theline 9-9, shown in FIG. 8.

FIG. 10 is an exploded view of a pivoting post and a magnet attachedthereto, which are fixedly attached to the base of the data storageapparatus.

FIG. 11 is an exploded view of a pair of support arms and an electricalcoil assembly therebetween which is a portion of the pivot assembly ofthe data storage apparatus of the present invention.

FIG. 12 is an exploded view of the coil assembly portion of the supportassembly shown in FIG. 11.

FIG. 13 is a cross-sectional view through the coil and magnet portionshown in FIG. 9 and through the plurality of data storage discs attachedto the spindle and the motor which drives the spindle.

FIG. 14 is a partial, cross-sectional view of the support assembly shownin FIG. 9, showing the protrusion attached to the coil assembly.

FIG. 15 shows two stop posts and a spring wound about the pivoting postwith the protrusion of the coil assembly resting against one end of thespring.

FIG. 16 is a top view of the disc storage apparatus of the presentinvention showing a transducer head having its skew angle adjusted suchthat it is tangent to the radius of the data storage disc at one of theradius distances.

FIG. 17 is a schematic view of the geometry of the disc storageapparatus of the present invention, with the various parameters whichare used in the calculation of the skew angle of the transducer head.

FIG. 18 is a graph showing the skew angle as a function of the radius ofthe data storage disc and the various constant height level graphs.

FIG. 19 is a graph of a Bode plot of the mechanical frequency responseof the disc storage apparatus of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, there is shown a disc storage apparatus 10 of thepresent invention. The disc storage apparatus 1? is shown with its coveroff exposing the various major elements of the disc storage apparatus10. The disc storage apparatus 10 comprises a base 12. Mounted on thebase 12 is a plurality of data storage discs 14(a..h). Although eightdata storage discs 14 are shown, clearly, the invention is not solimited in the number of data storage discs that can be used.

The data storage discs 14 are all mounted on a spindle 16 and are gangedfor rotation about the spindle 16 by a motor 18. The plurality of datastorage discs 14 are held in place on the spindle 16 by a retainingclamp 18. A center shaft 22 of the spindle 16 is fixedly attached to thecover (not shown), passing through the motor 18 and is fixedly attachedto the base 12.

The motor 18 has a coil 24 fixedly attached to the shaft 22. Surroundingthe coil 24 are permanent magnets 20 which are connected to the spindle16. When coil 24 is energized, electromagnetic forces cause the magnet20 and the spindle 16 attached thereto and the data storage discs 14 torotate relatively to the center shaft 22. The motor 18 is ofconventional design.

Each of the data storage discs 14 is made of a substrate material, suchas glass, on which is deposited a magnetically susceptible materialwhose magnetic domains can change under the influence of locally-appliedmagnetic forces. The retaining clamp 18 is in the shape of a ring with acentral hole 30 and a plurality of spaced-apart teeth-shaped members 32positioned circumferentially about the ring. The teeth-shaped members 32protrude into the central hole 30. The retaining member 18 is ofconventional design and has been used by automotive and agriculturalequipment to hold members onto a rod, and is available from company suchas Walds Truarch.

Referring to FIG. 5, there is shown a partial, cross-sectional view ofan insertion tool 32 used to assemble the retaining member 18 onto thespindle 16. During the assembly process, the retaining clamp 18 is urgedin an axial direction, shown by the arrow A, along the axis of thespindle 16. The insertion tool 32 is urged along the ring portion of theretaining clamp 18. The hole 30 of the retaining clamp 18 is positionedover the spindle 16 and as the retaining clamp 18 is urged axially alongthe axis of the spindle 16, each of the teeth-shaped member 32 comesinto contact with the end of the spindle 16 and is moved in a directionshown by the arrows B. The retaining clamp 18 is placed in a retainingposition when the retaining clamp 18 abuts the topmost data storage disc14a. When the retaining clamp 18 is in the retaining position, each ofthe tooth-shaped members 32 is urged against the side of the spindle 16.This is shown in FIG. 4.

The use of the retaining clamp 18 to clamp the plurality of disc 14provides the following advantages. The amount of clamping force by theretaining clamp 18 against the plurality of disc 14 is controlled by theforce that is applied by the insertion tool 32 in the axial direction,when the retaining clamp 18 is inserted on the spindle 16. Thus, thedegree of force is controlled by the insertion tool 32. The plurality ofdiscs 14 can be clamped with a relatively light force for balancing. Forexample, discs can be purposely shifted to obtain correct dynamicbalance, when a light force is applied by the retaining clamp 18. Oncethe balance is determined, a final application of force by the insertiontool 32 can be made onto the retaining clamp 18 to increase the clampingforce. Further, the retaining clamp 18 provides flat spring constant tomaintain substantially constant force to the plurality of discs 14during temperature cycle. The uniform clamping force that is applied tothe plurality of discs 14 eliminate stress concentration so as not tobreak a disc 14 whose substrate is made of fragile material, such asglass. Compared to a conventional screw for attachment, the use of theretaining clamp 18 provides for maximum stiffness and uniform loaddistribution which allows the use of large spindle bearings whichimproves spindle runout, spindle stiffness and spindle life. Inaddition, compared to the conventional screw, there is no contamination,when the retaining clamp 32 is used.

Referring to FIG. 6, there is shown a removal tool 34 which can be usedto remove the retaining clamp 18 from the spindle 16. The removal tool34 has a plurality of hook-shaped members 36. Each of the hook-shapedmembers 36 has a width which is narrower than the spacing between a pairof adjacent teeth-shaped members 32. Thus, the hook-shaped members 36can be inserted into the space between the adjacent teeth-shaped members32. The removal tool 34 is then rotated by an amount such that a portionof the hook-shaped member 36 is between the teeth-shaped member 32, thedisc 14a and the spindle 16. An axial force is then used to move each ofthe teeth shaped members 32 away from the side of the spindle 16 and tolift the retaining clamp 18 in an axial direction away from the spindle16. In this manner, the retaining clamp 18 is thus removed from thespindle 16.

The disc storage apparatus 10 also comprises a pivoting post 40. Thepivoting post 40 is cylindrically-shaped and is substantially hollow onthe inside (see FIG. 10). The pivoting post 40 is attached to a planarmember 42 which is substantially in the shape of a letter L. Along thebase portion 44 of the planar member 42 is a permanent magnet 46. Thepermanent magnet 46 has substantially a rectangularly-shapedcross-section. The planar member 42 is fixedly attached to the base 12and the cover 21 by the screws 23(a,b,c). Thus, the pivoting post 40 isalso fixedly attached with respect to the base 12. An upper-casing 48aand a lower-casing 48b encase the magnet 46, providing for the cavities49a and 49b, between the magnet 46 and the upper case 48a and the lowercase 48b, respectively. Collectively the cavities 49a and 49b serve as aregion in which the coil 60 (discussed hereinafter) is positioned. Theplanar member 42 also comprises two stop posts: 45a and 45b, which arecylindrically-shaped members spaced apart from the pivoting post 40. Thefunction of these stop posts 45a and 45b will be discussed hereinafter.

The disc storage apparatus 10 also comprises a pivoting assembly 50(shown in FIG. 11). The pivoting assembly 50 comprises an axial post 52which is substantially cylindrically shaped. The axial post 52 ispositioned within the pivoting post 40 and is pivotally rotatably aboutthe pivoting post 40. At one end of the axial post 52 (the upper end) isa first supporting member 54a connected thereto. A second supportingmember 54b, substantially congruent in shape to the first supportingmember 54a, is attached to the axial post 52 at the other end thereof.Each of the supporting members 54a and 54b has one end 56 connected tothe axial post 52. The other end 58 of the supporting member is free topivot about the fixed end 56. Between the pivotally movable end 58 andthe fixed end 56, the supporting member 54 is substantially curved inshape having an arcuate region 60.

Within the arcuate region 60, i.e., substantially along a line definedfrom the pivoting end 58 to the fixed end 56, and substantially near thecenter of percussion of the pivoting assembly 50, is attached a coilassembly 60. As shown in FIG. 12, the coil assembly 60 comprises a coil62 which has a cross-sectional shape that is substantially rectangularin shape. Two coil supporting members: 66a and 66b are position to eachside of the coil 62 and are fixedly attached to the support members 54aand 54b of the pivoting assembly 50. Within the rectangularly-shapedcross-section of the coil 62 is a rectangularly-shaped cross-sectionalhole 64 in which is positioned the magnet 46. Thus, as the coil 62 isenergized, it exerts a force with respect to the magnet 46 causing thepivoting assembly 50 to pivot about the pivoting post 40.

The coil assembly 60 also comprises a protruding member 70 which isconnected to one end of one of the coil supporting member 66a. Woundabout the pivoting post 40 is a spring 72. The spring 72 is wound aboutthe pivoting post 40, such that it comes to rest against the stop posts45a and 45b. The spring 72 has a tension force shown in the direction ofthe arrow C, as shown in FIG. 15. The spring 72 has two ends, each ofwhich extends beyond the stop posts 45a and 45b. The protruding member70 of the coil assembly 60 lies in the region between the ends of spring72 and moves therebetween. However, if excessive electrical power isapplied to the coil 62 causing excessive magnetic force to be generatedin either direction, the coil 62 and the protruding member 70 would cometo rest against one of the ends of the spring member 72. Since thespring 72 is resilient but has an urging force, the coil 62 would beopposed by a resilient force. In this manner, the spring 72 acts as astop to prevent the coil 62 from moving excessively in either directionbeyond the intended limits of operation. The use of the spring 72prevents damage to the coil assembly 60 in that no fixed stop isprovided. Instead, the coil assembly 60 is allowed to come to restagainst an urging force that increases as the coil 62 attempts toincrease beyond its limits.

When the coil assembly 60 is activated and the pivoting assembly 50 ismoved about the pivoting post 40, the upper supporting member 54a passesover the topmost layer of the data storage discs 14a (see FIG. 2),whereas the lower supporting member 54b passes under the bottom mostdata storage disc 14h (as shown in FIG. 13). Further, when the pivotingassembly 50 is so moved, the force compresses the upper and lowersupporting members 54a and 54b along the legs 59a and 59b of the members54a and 54b.

A transducer head assembly 80 (generally shown in FIGS. 1, 2, 8 and aportion of it (transducer head block 84) is shown in FIG. 11) isattached to the pivoting end of the pivoting assembly 50. The transducerhead assembly 80 has a plurality of transducer arms 82 withsubstantially one arm per data storage disc 14. All of the arms 82 areattached to the transducer head block 84 by an adjustable screw 86. Thearms 82 extend generally in a radial direction with respect to each ofthe data storage discs 14. At the end of each of the transducer arms 82is a transducer head 84. The transducer heads 84 also extend in a lineardirection from the transducer arm 82. The adjusting screw 86 can be usedto change the skew angle of each of the transducer heads 84 with respectto the tangent to the radius of each of the data storage discs 14. Asthe coil assembly is energized and as the pivoting assembly 50 pivotsabout the pivoting post 40, the transducer arms 82 move generally froman inner radius to an outer radius or vice versa.

The disc storage apparatus 10 is particularly adapted and is suitablefor recording data on the magnetic media on each of the data storagediscs 14 in "tracks", which are cylindrically-shaped concentric ringsabout the data storage discs 14. Further, the data storage apparatus 10is particularly suited for recording in what is known as zone bandrecording format. In zone band recording, data is recorded at differentdensities at different radii resulting in a constant number of bits orbytes for each track. However, zone band recording requires that eachtransducer head 84 be maintained at a constant height above a datastorage disc 14.

In the disc storage apparatus 10 of the present invention, each of thetransducer heads 84 is maintained at a constant flying height above itsassociated data storage disc 14. This is accomplished in the followingmanner.

Referring to FIG. 17, there is shown a schematic view of the geometry ofthe disc storage apparatus of the present invention, with the variousparameters which are used in the calculation of the skew angle of thetransducer head.

The definitions used for FIG. 17 are:

a=Distance from center of pivot to center of radius

r=Radial distance from the pivot to the head:

r₁ =inside head;

r₀ =outside head

R=Track radius

∴=Cylinder slope

δ=Head slope ##EQU1##

In the present invention, the data storage apparatus 10 employs datastorage discs 14 that generally have a radius of approximately 1.87inches (4.75 centimeters). The base 12 generally has the dimensions of4.00 inches×5.75 inches (10.16 cm×14.61 cm). The apparatus 10 has aheight of approximately 1.62 inches. The pivoting post 40 is generallylocated at minus 3.0 inches from the center of radius of each of thedata storage discs 14. This is in a location on the base 12 that issubstantially the furthest point away from the center of the radius forthe discs 14. With the pivoting post 40 so located, the distance "a"between the pivoting post 40 and the center of the radius of the datastorage disc 14 is substantially at a maximum. With r equal to 2.98inches (7.57 centimeters) representing the distance from the pivotingpost 40 to the transducer head 84 in a radial direction, the variablesshown in FIG. 17 would have the following values.

    __________________________________________________________________________    R X    Y   THETA                                                                              GAMMA THETA-GAMMA                                                                             SKEW                                          __________________________________________________________________________    1.0                                                                             -0.18660                                                                           0.98244                                                                           10.75443                                                                           -70.7509                                                                            81.50529   -8.0000                                      1.2                                                                             -0.25993                                                                           1.17151                                                                           12.51006                                                                           -66.8510                                                                            79.36104  -10.1442                                      1.4                                                                             -0.34660                                                                           1.35642                                                                           14.33385                                                                           -62.9239                                                                            77.25774  -12.2475                                      1.6                                                                             -0.44660                                                                           1.53641                                                                           16.20799                                                                           -58.9642                                                                            75.17222  -14.3331                                      1.8                                                                             -0.55993                                                                           1.71069                                                                           18.12397                                                                           -54.9663                                                                            73.09025  -16.4150                                      __________________________________________________________________________

As can be seen from the above, at R=1.0, the value of "theta-gamma" is81.50529 degrees. If -89.50529 degrees were added to the value of"theta-gamma", the resultant "skew" angle would be -8.000 degrees. Ifthe same value of -89.50529 degrees were added to each of the respectivevalues "theta-gamma", the result would be the degree shown under thecolumn "skew". In short, if a constant number of degrees was added toeach of the values of "theta - gamma" at various R settings, the skewangles would have the resultant values, as set forth in the above table.

The constant angle is accomplished by changing the adjusting screw 86,such that the transducer head 84 would have the resultant skew angle of-8.000 degrees when R=1.0. Thus, as shown in FIG. 16 which shows thetransducer head 84 at a distances of substantially R=1.0, the adjustingscrew 86 can be adjusted such that the transducer head 84 is positionedwith a skew angle of -8.000 degrees with respect to the tangent to theradius R at 1.0. When the transducer head 84 is so set, the transducerhead 84 would then have a skew angle as shown in the above table forother values of R. That is, as R increases, the skew angle alsoincreases.

FIG. 18 shows a graph of skew angle versus radius of the disc. Furtherit shows the constant flying height contours. From FIG. 18, it can beseen that, based upon the particular geometry of the present discstorage apparatus 10, wherein the pivoting post 40 is at a largedistance away from the center of the radius of the data storage discs14, the resultant skew angle at different radii R would result in thetransducer heads 84 flying at a substantially constant height of 5microinches. In short, by varying the skew angle as a function of thedistance of R, a substantially constant flying height of the transducerhead 84 with respect to the surface of each of the data storage discs 14can be maintained. In this manner, zone band recording can beaccomplished.

There are many advantages to the data storage apparatus 10 of thepresent invention. First, by having a support member 54 having anarcuate region between its ends, when the pivoting assembly 50 ispivoted about the pivoting post 40, greater mechanical stability isachieved. This results in greater frequency response. A Bode plot of thefrequency response of the data storage apparatus 10, shown in FIG. 19,shows that the apparatus 10 is devoid of any high gain frequencyresonances.

Secondly, by using a retaining clamp 18, discs 14 can be made out offragile material, such as glass. Further, the retaining clamp 18provides greater uniform load distribution with far less contaminationof the discs 14 compared to a conventional screw during the clamping andremoval process.

Finally, by being able to change the skew angle of the transducer head84 relative to the tangent to the radius of the disc 14, the transducerhead 84 can be maintained at a substantially constant flying height,resulting in zone band recording.

The theoretical basis of the invention can be understood as follows. Theproblem to be solved in the apparatus 10 of the present invention is toposition, in a very short time span, a magnetic transducer, accuratelyand in a dynamic fashion, over a track on a rotating disc. The majorcomponents of the tolerance affecting accuracy are:

1. Accumulation of tolerances from many parts (so called stack-up ofmechanical parts);

2. Temperature;

3. Interchangeability;

4. Dynamics (pull in, spindle runout, vibration);

Improved performance (i.e. cost, capacity, access time) can be obtainedby increasing track density (tracks per inch TPI) to the limitscontrolled by the components affecting head positioning tolerances.

One of the prior art improvements in disc drive performance was theapplication of servo control. The electrical signal is transduced fromthe disc surface to a magnetic head, transformed to an amplifiedelectrical current, then transmitted to a voice coil motor (VCM) whichcaused precise movement of the transducer head. This technologyeliminated virtually all static tolerances for head positioning used inopen loop type drives, such as stepper motor or mechanical detenting forposition control. (There exists a class of drives which utilize anexternal from the disk, a position transducer such as a glass reticuleassociated with a VCM. These drives can have reduced access time but notsubstantially improved position control.)

With static tolerances virtually controlled, the designer of a discdrive must concentrate not only on the static tolerances but also thedynamic tolerances. The goal now becomes to improve servo control toreduce the dynamic tolerances. The desired method for improved servocontrol is to increase gain.

The technique most commonly used to measure the dynamic quality of amechanical design is the Bode plot. This is a plot of (output of headposition/input of coil current) vs. frequency. A good Bode plot will bedevoid of High Q mechanical resonances, i.e. peaks in the curve.

With a good Bode plot, high servo loop gain can be achieved and thefollowing advantages will be obtained:

1. Fast, crisp, actuator response;

2. Minimization of undershoot and overshoot;

3. Good servo stability;

4. Immunity from external vibration;

5. Ability to follow non-repeatable spindle runout.

To prevent in-line mechanical resonances, thereby obtaining a good Bodeplot, the following design rules should be observed:

1. Avoid applying in-line forces through ball bearings;

2. Avoid bending structural members; structural members can becompressed or tensioned;

3. Position or couple forcing elements close to the transducing elements(heads);

4. Avoid cantilevered masses;

5. Mount spindle and actuator from both sides (top and bottom of baseplate).

To obtain a good Bode plot, the mechanical designer must obey all theabove design rules.

There are two basic types of positioners, linear (moving in a straightline) and rotary. The characteristics of each are as follows:

Linear:

1. Good frequency response (good Bode plot);

2. Requires large space;

3. Expensive;

Rotary:

1. Prior Art design has poor frequency response;

2. Lower cost;

3. Requires less space than linear positioners;

A recent development in the industry is the introduction of zone bandingrecording. This requires nearly constant flying height. Constant flyingheight can be achieved by selecting a drive geometry to match the flyingcharacteristics of the slider. This is done by placing the pivot centerin relation to the spindle center and the head radius in such a mannerthat the correct head skew angle as a function of the track radius isachieved. This is an advantage of the rotary positioner over a linearpositioner. The linear positioner cannot achieve constant flying height.

Since the 31/2 inch standard size drive does not allow sufficient roomfor a linear positioner using a VCM actuator, a rotary positioner mustbe used. Heretofore, all of the prior art 31/2 inch drive with VCMpositioners have suffered from failure to observe all of the designrules set forth hereinabove. For example, most have been designed withthe VCM actuator at one end of a member, with the transducing elementsat another end of the member and with a ball bearing pivot therebetween.This violates rule number one. Others, such as those disclosed in U.S.Pat. Nos. 4,300,176 and 4,751,597, have used cantilevered masses, whichviolate rule #4. In short none have been satisfactorily designed withresulting good Bode plots.

What is claimed is :
 1. In a disc storage apparatus having a spindlewith a central axis, a plurality of data storage discs mounted on saidspindle, and motor means connected to said spindle for rotating saiddiscs, wherein the improvement comprising:a retaining member in theshape of a ring with a central hole and a plurality of spaced-aparttooth-shaped members positioned circumferentially about said ringprotruding into said central hole; said retaining member positioned withsaid spindle through said central hole, with said retaining membersubstantially abutting one of said data storage discs, with saidplurality of tooth-shaped members urging against a side of said spindlesubstantially parallel to said central axis thereby clamping said datastorage discs by said tooth-shaped members urging against said side. 2.The apparatus of claim 1, wherein said discs are made of glass.
 3. Adisc drive comprising:a base; a spindle having an axis; a plurality ofdata storage discs mounted on said spindle; motor means on said base,connected to said spindle for rotating said discs about said axis; aretaining clamp in the shape of a ring with a central hole and aplurality of spaced-apart tooth-shaped members positionedcircumferentially about said ring protruding into said central hole;said retaining clamp positioned with said spindle through said centralhole, and substantially abutting one of said data storage discs withsaid plurality of tooth-shaped members urging against a side of saidspindle substantially parallel to said axis thereby clamping said datastorage discs by said tooth-shaped members urging against said side. 4.The apparatus of claim 3, wherein said discs are made of glass.
 5. In anew use of a retaining member in the shape of a ring with a central holeand a plurality of spaced-apart tooth-shaped members positionedcircumferentially about said ring protruding into said central hole,wherein said method comprising:inserting said retaining member over aspindle of a disc drive having a central axis with a plurality of datastorage discs mounted therein, with said spindle through said centralhole, moving said retaining member in a direction substantially parallelto said central axis to said discs until said retaining member abutssubstantially against one of said data storage discs with said pluralityof tooth-shaped members urging against a side of said spindlesubstantially parallel to said central axis thereby clamping said datastorage discs by said tooth-shaped members urging against said side.